Buildbot: add script to update libraries and submodules

This is meant to replace the individual build steps for the various libraries
and submodules, so we can easily get the correct revisions associated with
different branches and releases.

build_files/buildbot/slave_update.py

@@ -0,0 +1,31 @@
+# ##### BEGIN GPL LICENSE BLOCK #####
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software Foundation,
+#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ##### END GPL LICENSE BLOCK #####
+
+# <pep8 compliant>
+
+import os
+import runpy
+
+# We run from build/ directory.
+blender_dir = os.path.join('..', 'blender.git')
+blender_dir = os.path.abspath(blender_dir)
+os.chdir(blender_dir)
+
+# Run make update which handles all libraries and submodules.
+make_update = os.path.join(blender_dir, "build_files", "utils", "make_update.py")
+runpy.run_path(make_update)